US president Barack Obama has said economic sanctions against Iran to contain Tehran's nuclear ambitions have "enormous bite," and he will consult with other nations on additional steps to ensure that Iran does not acquire an atomic weapon.

US President Barack Obama on the sidelines of the APEC summitPhoto: AFP/GETTY

7:00AM GMT 14 Nov 2011

Mr Obama expressed confidence that Russia and China in particular understand the threat of a nuclear armed Iran would pose and said their leaders agree that Iran cannot develop nuclear weapons and trigger a nuclear arms race in the region.

The president, answering questions at a press conference during an Asia-Pacific economic summit, did not specifically say he would consider military action if Tehran were to persist in arming itself with a nuclear weapon. But he added: "We are not taking any options off the table. Iran with nuclear weapons would pose a threat not only to the region but also to the United States."

A report on Friday from the International Atomic Energy Agency provided new evidence that Iran's nuclear program includes clandestine efforts to build a bomb. The report, circulated among the UN watchdog agency's member countries, includes satellite images, letters, diagrams and other documents. It alleges Iran has been working to acquire equipment and weapons design information, testing high explosives and detonators and developing compute models of a warhead's core. Taken together, it's the most unequivocal evidence yet that the Iranian program ranges far beyond enriching uranium for use in energy and medical research, which is what Tehran says it's for.

In meetings on Saturday with Russian President Dmitry Medvedev nor Chinese President Hu Jintao, Mr Obama sought to rally support for putting new pressure on Iran's regime. But there was little public sign either country was ready to drop its opposition to additional sanctions. Four rounds of UN sanctions have caused economic hardship in Iran, but have yet to force any change in the nuclear program.